Adding Water to Pressurized System

jebatty Posted By jebatty, Oct 24, 2009 at 1:09 PM

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  1. jebatty

    Minister of Fire

    Jan 1, 2008
    Northern MN
    Haven't seen a note on this, so might be helpful to those with pressurized systems and not connected to a water line. I have no water where my boiler is located, so I have to add water manually when needed (rarely, usually only when I want to work on the system). An easy way to de-pressurize the system to add water or otherwise work on the system is to have a shut-off valve on the pressure tank, and then when the system is hot, fire out, turn the valve off. The system pressure will fall to 0 or less as the system cools (might suck in some air) because the pressure tank will not release its stored water, you can work on the system, and additional water can easily be added to a high fill point. When finished adding water, close the fill valve, open the pressure tank valve, and the system is instantly re-pressurized, and any air admited is expelled through the vents.
  2. RobC

    Minister of Fire

    Jul 28, 2009
    Foxboro MA
    Good timing with this tidbit. I was just going to clean and treat my WB, OB & 1000 gallon storage and now I won't have to fuss with 100G expansion tank balancing. Will still have to give it a rinse before final fill.


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  3. WalkGood

    New Member

    Oct 26, 2009
    Isle of Long
    Hopefully you have a low water cutoff installed?
  4. Tony H

    Tony H
    New Member

    Oct 24, 2007
    N Illinois
    I have a fill valve but have found when adding or restoring glycol mix to the boiler I use a drain valve piped in at the back of the boiler and a utility pump.
    Just open the valve and turn on the pump to pump in from 5 gal bucket and when empty shut the valve and turn off the pump. Just do the pump on/off and valve open/closed at the same time or the drain water will out flow to the pump. No reason you couldn't use this same setup to just add water if there is no fill valve installed.
    Another note my fill valve is not near the boiler it's in the basement near where the furnace and DHW are located and I also have a drain there if needed
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